[orthoxerox]

As the joke goes, one morning Livshitz was riding a tram to work, someone pushed him and he dropped his manuscript into the mud, ruining a few pages. When he arrived at the lab, he complained to Landau that he would have to spend the whole day rewriting the proof of a tricky theorem because the middle part was now gone, but Landau suggested simply to put "from which it is obvious that" there instead.